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Re: TC Inductance Formulas...

To: teslaatgrendel.objincdotcom

Subject: Re: TC Inductance Formulas...

From: tchandatslipdotnet (Tim Chandler)

Date: Fri, 16 Feb 1996 19:25:06 0500

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<snip>
>I've been using Wheeler's with a slight modification for helical
>coils. Instead of a bottom line = 9r + 10h, I've been using a
>bottom line = 10(r + h). It seems slightly better for typical
>Tesla secondaries. In any case, Wheeler seems to come within about
>5% worst case and often better in my experience.
>
>Malcolm
>
Sorry for getting this out so late but my outgoing mail has been down...
I personally like the most exact inductance calculation I can get, but my
problem is that out of 7 different formulas I have used to calculate the
inductance of the secondary, only six are even near close to one another
(one is completely off at about 23mH while the others range from 26mH to
29mH). Here is what I have calculated using the different formulas (i1)  (i7):
For a 6" TC...w/out discharge toroid
Inductance Calculations
(H) (mH) (uH)
L: (i1) 0.026275632 26.275631704 26275.631704
(i2) 0.026275632 26.275631704 26275.631704
(i3) 0.029201946 29.201945986 29201.945986
(i4) 0.026295601 26.295601184 26295.601184
(i6) 0.029193514 29.193514397 29193.514397
(i7) 0.029193514 29.193514397 29193.514397
L:(Average) (SUM) 0.166435839 166.43583937 166435.83937
(AVG) 0.027739307 27.739306562 27739.306562
The above is the inductance calculated using only the diameter of the coil
from itself, nothing else is taken into acount.
L[m]: (i1) 0.026507712 26.507711770 26507.711770
(i2) 0.026507712 26.507711770 26507.711770
(i3) 0.029473178 29.473177587 29473.177587
(i4) 0.026527858 26.527857631 26527.857631
(i6) 0.029464668 29.464667684 29464.667684
(i7) 0.029464668 29.464667684 29464.667684
L[m]:(Average) (SUM) 0.167945794 167.94579413 167945.79413
(AVG) 0.027990966 27.990965688 27990.965688
The above L[m] is calculated using the mean radius or mean diameter, that
being the radius measured from the center of the coil form to center of
conductor in the winding.
L[p]: (i1) 0.026296048 26.296047897 26296.047897
(i2) 0.026296048 26.296047897 26296.047897
(i3) 0.029225799 29.225799111 29225.799111
(i4) 0.026316033 26.316032893 26316.032893
(i6) 0.029217361 29.217360635 29217.360635
(i7) 0.029217361 29.217360635 29217.360635
L[p]:(Average) (SUM) 0.166568649 166.56864907 166568.64907
(AVG) 0.027761442 27.761441511 27761.441511
The above L[p] is a "prime" calculation, I am trying to determine which
method is closest to the actual measured inductance of the coil. The
"prime" measurement is taken from the inner side of the conductor, thus it
accounts for the coil form diameter plus the build or thickness of the
insulator/polymer on the magnet wire, in this particular case it was
calculated using double build #22AWG Heavy Armored PolyThermaleze (BELDEN).
The first insulator coat is CrossLinked Modified Polyester (8.167e4 in
thick) and the second insulator coat is an AmideImide Polymer (4.083e4 in
thick). In total with the conductor and the insulation build the magnet
wire has a diameter of 2.78e2in.
Sorry if the above calculations seem alittle weird or eccentric, but I am a
scientist and I generally quest for perfection in my work.
Note how the ranges vary, and actually the average of the "prime"
calculation is the closest to the inductance I have calculated by using the
measured resonace frequency. I myself didn't actually measure the resonant
frequency, I had a ECE graduate student at the university do it, I beleive
he used a signal generator and a scope,as well as a resistance, all in
series with the inductor, at least I think that is what he said. Anyway he
said he had and could do it so I let him. If this measured resonance is in
error please let me know, power and propulsion physics is my forte, not
electrical engineering so to speak.
Any suggestions or comments...
Tim
oooo
 Timothy A. Chandler  M.S.Physics/B.S.Chmeistry 
oooo
 NASALangley Research Center  George Mason University 
 Department of Energy  Department of Physics 
 FRT/Alpha  NASALaRC/DOE JRD/OPM  Department of Chemistry 
 CHOCT FR Designation #82749156/MG09 OPCEFC 
oooo
 Private Email Address: tchandatslipdotnet 
oo